A Research Of Passive Circuit And Antenna Based On SSPP

As a special surface waves,surface plasmon polaritons(SPP)have been extensively studied and used in the optical frequency region.Because the metallic negative permittivity at the optical frequency,the SPP can be tightly bounded on the interface of a metal and dielectric with exponential decay in the direction normal to the interface.However,in virtue of the perfect electric conductors(PEC)of the meatal at terahertz and microwave bands,the natural SPP mode cannot exist at those frequencies.In order to obtain the plasmon propagation at these frequencies,the spoof surface plasmon polaritons(SSPP)were proposed by researchers.At the same time,the structure that supports the SSPP modes were called SSPP waveguide.Based on the study of predecessor,we make a thorough research about the application of SSPP in aspect of the passive circuits and antenna.This paper has carried out mainly the following aspects of work:Firstly,a novel transition structure from microstrip line to SSPP waveguide is proposed in this paper.The symmetrically flaring ground and gradient groove are used to solve the problem of transverse and longitudinal conversion of electromagnetic field and mismatch of wave vector under two different modes.At last,a good broadband transitional structure in the frequency range of 3.22 to 6.27 GHz is achieved.Secondly,we studied the second resonant mode of the vertical spling ring resonator(VSRR),which can be excited by the electric filed perpendicular to the metallic surface of the VSRR.In the meatime,we used SSPP to excite the second resonant mode of VSRR for the first,resulting in the rejection of the SPP mode at the resonant frequency.Finally,a dual-frequency is designed and fabricated.The transmission coefficients are less than-15 dB in the frequency range of 6.67 to 6.97 GHz and 8.16 to 8.64 GHz,which correspond to the relative bandwidths of 4.39% and 6.89%,respectively.A broadband rejection filter are designed and fabricated.The measured-20-dB transmission coefficient bandwidth is from 8.15 to 10.2 GHz,which correspond to the relative bandwidths of 22.34%.Then,we find that the SSPP has a characteristic of high frequency cutoff by analyzing the dispersion relation of SSPP,which means that the SSPP cannot propagate when the working frequency is higher than the cut-off frequency.By using this property,a SSPP-based circular patch antenna with wideband harmonic rejection is presented.The results show that the prototype antenna has an impedance bandwidth(|S11|<-10 dB)from 3.0 to 3.8 GHz(24%)and suppress the second,third and fourth harmonic up to-1 dB.Finally,a broadband end-fire antenna with high gain and direction is presented by loading the SSPP waveguide on the radiation direction of a wideband end-fire antenna.The SSPP waveguide can be excited by the original wideband end-fire antenna and achieve high efficient radiation by converging electromagnetic wave.